Method for regulating and controlling volatility and non-volatility of ferroelectric device

Abstract

The invention relates to a method for regulating and controlling the volatility and non-volatility of a ferroelectric device. The method comprises the following steps: setting the ferroelectric layer thickness, the dielectric layer thickness, the ferroelectric layer dielectric constant and the dielectric layer dielectric constant of the ferroelectric device based on property requirements; external electric excitation is connected to the ferroelectric device, and the ferroelectric device is controlled to present the volatile or non-volatile property corresponding to the property requirement; and if the property requirements change, resetting the ferroelectric layer thickness, the dielectric layer thickness, the ferroelectric layer dielectric constant and the dielectric layer dielectric constant of the ferroelectric device. Compared with the prior art, the method has the advantages that the universality of ferroelectric devices is improved, and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of ferroelectric devices, and in particular to a method for regulating volatility and non-volatility of ferroelectric devices. Background Art

[0002] Ferroelectric materials are a type of material that exhibits the ferroelectric effect. Under an applied electric field, the electric dipoles inside the material are oriented and produce spontaneous polarization; the polarization direction can be modulated by the applied electric field, and non-volatile residual polarization still exists after the electric field is removed. This property makes ferroelectric materials have important application value in fields such as memory devices. For example, ferroelectric random access memory (FeRAM) can be made, which has the advantages of fast read and write speed, low power consumption, and high reliability; ferroelectric tunnel junction (FTJ) devices can be made by utilizing the modulation effect of different polarization directions on the potential barrier; ferroelectric materials are used as the gate dielectric layer in transistors, and the channel resistance can be adjusted by changing the polarization state, so that ferroelectric field effect transistors (FeFET) can be made. In recent years, with the development of nanotechnology and thin film preparation technology, the research on ferroelectric materials at the micro-nano scale has received widespread attention, providing new possibilities for their application in the field of electronic devices.

[0003] Ferroelectric devices use polarization states to store data, and their ability to store data is measured by how long the polarization is maintained. Depending on the length of the data retention time, they can be divided into volatile and non-volatile devices, each with different application scenarios. For example, non-volatile devices can be used for data storage and synaptic devices in neural networks, while volatile devices can be used for artificial neurons and reserve pool computing.

[0004] However, ferroelectric devices can generally only maintain volatility or non-volatility, so their application in synaptic devices or artificial neurons and reservoir computing is limited. Summary of the invention

[0005] The purpose of the present invention is to provide a method for regulating the volatility and non-volatility of ferroelectric devices in order to improve the scope of application of ferroelectric devices. By changing the properties of the ferroelectric layer FE and the paraelectric dielectric layer IL in the device, especially the thickness t and the dielectric constant ∈, the polarization loss rate can be regulated, thereby adjusting the ferroelectric device to be volatile or non-volatile.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for regulating volatility and non-volatility of a ferroelectric device, the method comprising the following steps:

[0008] The ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are set based on the property requirements;

[0009] Connecting an external electrical stimulus to the ferroelectric device to control the ferroelectric device to exhibit volatility or non-volatility corresponding to the property requirements;

[0010] If the property requirements change, the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are reset.

[0011] Furthermore, the property is required to be volatile or non-volatile.

[0012] Furthermore, if the property requirement is changed from volatility to non-volatility, the specific steps of resetting the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are as follows:

[0013] One or more steps of increasing the thickness of the ferroelectric layer, decreasing the thickness of the dielectric layer, increasing the dielectric constant of the dielectric layer, or increasing the dielectric constant of the ferroelectric layer are performed until the polarization loss rate is less than a rate threshold, at which time the ferroelectric device is nonvolatile.

[0014] Furthermore, if the property requirement is changed from non-volatile to volatile, the specific steps of resetting the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are as follows:

[0015] One or more steps of reducing the thickness of the ferroelectric layer, increasing the thickness of the dielectric layer, reducing the dielectric constant of the dielectric layer, or reducing the dielectric constant of the ferroelectric layer are performed until the polarization loss rate is greater than or equal to a rate threshold, at which time the ferroelectric device is volatile.

[0016] Furthermore, the polarization loss rate is the first-order derivative of the ferroelectric polarization intensity with respect to time, and the ferroelectric polarization intensity is:

[0017] P FE +∈ FE E FE =∈ IL E IL

[0018] Among them, P FE Ferroelectric polarization strength, ∈ FE and ∈ IL are the dielectric constants of the ferroelectric layer and the paraelectric layer, respectively, and E FE is the electric field strength of the ferroelectric layer, E IL is the electric field strength in the paraelectric layer.

[0019] Furthermore, the ferroelectric device includes an electrode M1, an electrode M2, a ferroelectric layer FE and a paraelectric layer IL.

[0020] Furthermore, the electrode M1 and the electrode M2 ​​are arranged on two sides of the ferroelectric device.

[0021] Furthermore, the ferroelectric device is connected to external electrical excitation by: connecting an external power source to the electrode M1 and the electrode M2.

[0022] Furthermore, when the ferroelectric device is connected to an external electrical excitation, the ferroelectric layer FE and the paraelectric layer IL are equivalent to two capacitors connected in series to divide the voltage.

[0023] Furthermore, the polarization loss rate is determined based on a set ferroelectric layer thickness, a dielectric layer thickness, a ferroelectric layer dielectric constant, and a dielectric layer dielectric constant of the ferroelectric device.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention can achieve regulation of polarization loss rate by changing the properties of the ferroelectric layer FE and the paraelectric dielectric layer IL in the device, especially the thickness t and the dielectric constant ∈, thereby adjusting the ferroelectric device to be volatile or non-volatile, and further allowing the device to adjust its applicable scope by adjusting the thickness t and the dielectric constant ∈ of the ferroelectric layer FE and the paraelectric dielectric layer IL, thereby improving the versatility of the ferroelectric device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of the ferroelectric device of the present invention;

[0027] Figure 2 The curve of the ferroelectric polarization intensity changing with the electric field of the ferroelectric layer of the present invention;

[0028] Figure 3 is the polarization state decay curve over time of the present invention;

[0029] Figure 4 The relationship between the polarization holding time and the thickness of the ferroelectric layer and the thickness of the paraelectric layer of the present invention;

[0030] Figure 5 This is the relationship between the polarization retention time and the dielectric constant of the paraelectric layer of the present invention. DETAILED DESCRIPTION

[0031] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0032] The present invention proposes a method for regulating volatility and non-volatility of a ferroelectric device. The ferroelectric device of the present invention comprises an electrode (M1), a paraelectric dielectric layer (IL), a ferroelectric dielectric layer (FE), and an electrode (M2). The specific preparation method is: a bottom electrode M1, a paraelectric dielectric layer IL, a ferroelectric dielectric layer FE, and a top electrode M2 ​​are sequentially grown on the surface of a substrate using a thin film deposition process, and then annealing is performed. The present invention can achieve regulation of the ferroelectric polarization retention characteristics by only selecting different materials and controlling the film thickness during the film preparation process, thereby preparing a device with volatility or non-volatility, thereby improving the versatility of the device. In addition, this method is applicable to various types of ferroelectric devices, such as ferroelectric random access memory (FeRAM), ferroelectric tunnel junction (FTJ), and ferroelectric field effect transistor (FeFET).

[0033] The method proposed by the present invention comprises the following steps:

[0034] The ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are set based on the property requirements;

[0035] Connecting an external electrical stimulus to the ferroelectric device to control the ferroelectric device to exhibit volatility or non-volatility corresponding to the property requirements;

[0036] If the property requirements change, the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are reset.

[0037] The property is required to be either volatile or non-volatile.

[0038] If the property requirement is changed from volatility to non-volatility, the specific steps of resetting the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are as follows:

[0039] One or more steps of increasing the thickness of the ferroelectric layer, decreasing the thickness of the dielectric layer, increasing the dielectric constant of the dielectric layer, or increasing the dielectric constant of the ferroelectric layer are performed until the polarization loss rate is less than a rate threshold, at which time the ferroelectric device is nonvolatile.

[0040] If the property requirement is changed from non-volatile to volatile, the specific steps of resetting the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are as follows:

[0041] One or more steps of reducing the thickness of the ferroelectric layer, increasing the thickness of the dielectric layer, reducing the dielectric constant of the dielectric layer, or reducing the dielectric constant of the ferroelectric layer are performed until the polarization loss rate is greater than or equal to a rate threshold, at which time the ferroelectric device is volatile.

[0042] The ferroelectric device of the present invention is Figure 1As shown, the ferroelectric device is a multilayer film structure, including an electrode (M1), a paraelectric dielectric layer (IL), a ferroelectric layer (FE), and an electrode (M2). app When the thickness of the paraelectric layer and the ferroelectric layer is t, the electric field E satisfies the following relationship:

[0043] V app =E FE t FE +E IL t IL

[0044] At the same time, since the device is a capacitive device, the multilayer films can be equivalent to a structure of multiple capacitors in series, satisfying the charge conservation relationship:

[0045] P FE +∈ FE E Fe =∈ IL E IL

[0046] Where P fE (E FE ) is the ferroelectric polarization intensity. Figure 2 As shown, the ferroelectric polarization intensity P FE With the electric field E FE Between P FE -E FE Hysteresis loop. ∈ FE and ∈ IL are the dielectric constants of the ferroelectric layer and the paraelectric layer respectively. The electric field strength of the ferroelectric layer is:

[0047]

[0048] Therefore, even if the external electric field is removed, the ferroelectric layer still has an electric field, and the direction of the electric field is opposite to the direction of ferroelectric polarization:

[0049]

[0050] This electric field will cause the ferroelectric polarization to gradually lose. Its rate is related to the ferroelectric switching rate. According to the Merz empirical formula, the polarization switching time of a single ferroelectric domain is:

[0051]

[0052] Its size is related to the characteristic reversal time τ0 and the activation electric field E act related to, and is affected by the electric field size E of the ferroelectric layer FE Modulation, with E FE When the voltage is reduced, the time required for the reversal is reduced. In the absence of an external electric field, the ferroelectric polarization decay curve with time is as follows: Figure 3 shown.

[0053] Therefore, by changing the properties of the ferroelectric layer FE and the paraelectric dielectric layer IL in the device, especially the thickness t and the dielectric constant ∈, the polarization loss rate can be controlled.

[0054] The time taken for the polarization intensity loss to reach 50% is defined as the polarization retention time. Figure 4 As shown, when the ferroelectric layer thickness t FE The thicker the paraelectric layer, the thicker the IL The thinner the film, the longer the polarization lasts, especially when t FE >>t IL When the ferroelectric layer thickness t FE The thinner the paraelectric layer thickness t IL The thicker the material, the longer the polarization will last, especially when t FE ≈t IL , the device is volatile. Figure 5 The polarization intensity loss varies with the dielectric constant ∈ IL The relationship between IL The smaller it is, the longer the polarization is maintained, and the device characteristics change from volatile to non-volatile.

[0055] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for regulating volatility and non-volatility of a ferroelectric device, characterized in that: The method comprises the following steps: The ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are set based on the property requirements; Connecting an external electrical stimulus to the ferroelectric device to control the ferroelectric device to exhibit volatility or non-volatility corresponding to the property requirements; If the property requirements change, the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are reset.

2. A method for controlling volatility and non-volatility of a ferroelectric device according to claim 1, characterized in that: The property is required to be either volatile or non-volatile.

3. A method for controlling volatility and non-volatility of a ferroelectric device according to claim 2, characterized in that: If the property requirement is changed from volatility to non-volatility, the specific steps of resetting the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are as follows: One or more steps of increasing the thickness of the ferroelectric layer, decreasing the thickness of the dielectric layer, increasing the dielectric constant of the dielectric layer, or increasing the dielectric constant of the ferroelectric layer are performed until the polarization loss rate is less than a rate threshold, at which time the ferroelectric device is nonvolatile.

4. The method for controlling volatility and non-volatility of a ferroelectric device according to claim 3, characterized in that: If the property requirement is changed from non-volatile to volatile, the specific steps of resetting the ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device are as follows: One or more steps of reducing the thickness of the ferroelectric layer, increasing the thickness of the dielectric layer, reducing the dielectric constant of the dielectric layer, or reducing the dielectric constant of the ferroelectric layer are performed until the polarization loss rate is greater than or equal to a rate threshold, at which time the ferroelectric device is volatile.

5. The method for controlling volatility and non-volatility of a ferroelectric device according to claim 1, characterized in that: The polarization loss rate is the first-order derivative of the ferroelectric polarization intensity with respect to time, and the ferroelectric polarization intensity is: P FE +∈ FE AND FE =∈ IL AND IL Among them, P FE Ferroelectric polarization strength, ∈ FE and ∈ IL are the dielectric constants of the ferroelectric layer and the paraelectric layer, respectively, and E FE is the electric field strength of the ferroelectric layer, E IL is the electric field strength in the paraelectric layer.

6. The method for controlling volatility and non-volatility of a ferroelectric device according to claim 1, characterized in that: The ferroelectric device includes an electrode M1, an electrode M2, a ferroelectric layer FE and a paraelectric layer IL.

7. A method for controlling volatility and non-volatility of a ferroelectric device according to claim 6, characterized in that: The electrode M1 and the electrode M2 ​​are arranged on two sides of the ferroelectric device.

8. The method for controlling volatility and non-volatility of a ferroelectric device according to claim 7, characterized in that: The ferroelectric device is connected to external electrical excitation by: connecting an external power source to the electrode M1 and the electrode M2.

9. The method for controlling volatility and non-volatility of a ferroelectric device according to claim 8, characterized in that: When the ferroelectric device is connected to external electrical excitation, the ferroelectric layer FE and the paraelectric layer IL are equivalent to two capacitors connected in series to divide the voltage.

10. The method for controlling volatility and non-volatility of a ferroelectric device according to claim 3, characterized in that: The polarization loss rate is determined based on the set ferroelectric layer thickness, dielectric layer thickness, ferroelectric layer dielectric constant and dielectric layer dielectric constant of the ferroelectric device.

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